1. Field of the Invention
The present invention relates generally to pumps and pump casings, and more specifically to casings for centrifugal pumps and pumps for use on emergency vehicles.
2. Background Information
Centrifugal pumps have been commonplace for ages, and have been used in numerous applications. The basic concept of a spinning impeller used to impart rotational forces coupled with a pump wall or volute to direct and increase the flow of a gas or fluid has spawned numerous useful products. Some of these products range from firefighting pumps to jet engines. Water-type pumps of many varieties use the centrifugal concept to generate a high pressure stream. Centrifugal pumps are particularly useful to the firefighting industry for producing high pressure flow and high flow rates to fight fires.
It is important to have versatile firefighting and emergency vehicles. One aspect of versatility is equipping such vehicles with high pressure outlets on either side of the vehicle. Such fire trucks have been around for decades. A midship fire truck, for instance, includes what is commonly known as a midship pump positioned relatively in the middle, or mid-ship, of the vehicle with outlets on either side. This allows the fire truck to park adjacent a fire hydrant or other source and conveniently connect to a water source from either side. Dual sided outlets also allow fluid from the vehicle to be pumped out either side for the convenience of delivery without having to turn around or greatly adjust the location of the vehicle. Dual outlets also allow for increased hook-ups to pump greater volume, if possible.
Midship pumps and other varieties of pumps, however, take up valuable space on an emergency vehicle. Providing a pump having a lower profile which takes up relatively little space would be an advantage so the unused space may be used for other important equipment or to construct a smaller vehicle for better maneuverability or other benefits. A smaller profile pump also accommodates for placement of the pump in a variety of areas on the vehicle, including, for instance, in the area under the cab portion of a vehicle (including the area beneath the rear passenger seat of a tilt-forward cab or cab-over-engine type of vehicle). Placement of a smaller profile pump in such area provides other benefits relating to overall design and overall systems design of such vehicles. Of course, such lower profile pumps must still satisfy the rigorous performance demands and outputs required by the industry.
The profile of a traditional firefighting pump is simply too large or awkward to be placed in an under-cab location of a vehicle without significant modification of the under-cab area and/or surrounding areas.
One example of a midship fire pump is shown with reference to FIG. 1 which depicts a Hale Type midship pump, manufactured by Hale Fire Pump Company, of Pennsylvania. FIG. 1 and detailed specifications pertaining to such pumps produced by Hale reveal the pump body 100 is horizontally split, on a single plane (represented generally by reference line 102), in two sections, an upper section generally shown with reference numeral 104, and a lower section generally shown with reference numeral 106. A stated purpose for these features is to accommodate easy removal of the entire impeller assembly including wear rings and bearings from beneath the pump without disturbing piping or the mounting of the pump in chassis. Detailed specifications further provide that the pump shall have one double suction impeller 108, and the pump body shall have two opposed discharge volute cutwaters 110 to eliminate radial unbalance.
As applicants understand the structure, the inner water path configuration of the pump shown in FIG. 1 is generally represented by the cut-away portion view shown in FIG. 2. Such water path structure allows for hookup to nozzles 112, 114 on both sides of the vehicle (vehicle not shown). It may be appreciated that closing of one nozzle 112 will result in all fluid output (i.e., output from each of the cut water areas) of the pump flowing to the opposing nozzle 114 or discharge valve (and vice versa). The discharge path 120 is configured so that closing one nozzle 112 or 114 (or opening only one of the nozzles 112, 114) will not close off fluid flow from either of the cut water paths 116, 118 of the centrifugal pump. A benefit of this path structure is to eliminate, or perhaps at least reduce, radial unbalance of the pump while accommodating outputs on either side of the vehicle. For instance, if fluid from one of the two cutwaters was otherwise not allowed to escape from a cut water path 116, 118, the rotational forces on the impeller would be out of balance which would tend to jeopardize the performance and life of the pump. One clear drawback of the above pump, however, is its large size, together with a relatively complicated water path structure and split design.
Accordingly, there is a need for a firefighting grade pump having a relatively modest profile so that the pump may occupy less area of a fire truck or other emergency vehicle, and where the pump includes nozzles on both sides of the truck. A modest profile is desired so that the pump may be located in the under-cab area of a vehicle. A simple single, non-split, casing design in which all water paths are located is also desired for ease of manufacture, hook-up and use. There is a need for such pump to be a powerful and reliable pump given the demands of the firefighting and emergency applications.